1. Field of the Invention
The present invention pertains to a method for determining adulteration of motor gasolines and similar hydrocarbon fuels by determining the presence of a marker dye in a small sample of the fuel with chromatography-grade silica which selectively extracts the dye from the fuel and is imparted with a color which is easily visually detected.
2. Background
The complexities involved in the production and distribution of automotive motor gasolines and similar fuels has given rise to the wide use of certain types of marker or identification additives or "dyes" in the fuels. For example, it is common to use both visible and non-visible identification dyes to distinguish one grade or octane rating of automotive gasoline from another grade. It has also become increasingly necessary, and may be legislatively mandated, that reformulated gasolines, i.e., those which are less likely to emit unwanted hydrocarbon vapors into the atmosphere or result in undesired combustion products, be identifiable from non-reformulated fuels. Moreover, the use of certain additives in automotive gasolines such as oxygenates, octane-enhancing additives and detergent additives increases the difficulty in testing the fuels to determine the presence of other additives such as brand or grade identification additives.
A process for testing of gasolines to determine the presence or concentration of an identifying additive associated with brand, grade or specific fuel composition should meet certain criteria. The test must be simple to perform in the field and require little, if any, sophisticated equipment. The test should require the use of as small a sample of the fuel as possible in order to minimize the hazards associated with handling the fuel and problems associated with disposal of the test sample. These desiderata are constantly being sought in the development of improved methods of testing automotive gasolines. However, the complex chemistry of automotive gasolines and the various additives and identification materials that are used in these fuels makes the achievement of the above-mentioned objectives particularly difficult.
By way of example, my U.S. Pat. No. 4,918,020, issued Apr. 17, 1990 and assigned to the assignee of the present invention, discloses and claims a method for analyzing marker dyes in automotive gasolines using solid-phase extraction onto a packed column followed by the formation of a colored complex in the column by reacting the separated marker dye with a color-forming reagent and then determining the color intensity of the colored complex to indicate the concentration of the marker dye in the fuel sample. Although this method is advantageous in certain respects, it does require the use of a separation column and test liquids which must be carried by the person performing the test in the field. Moreover, the particular method described in the '020 patent may not work with fuels which have been injected with certain additives such as oxygenates.
Another method of analyzing marker dye concentrations in petroleum fuels is described in U.S. patent application Ser. No. 07/825,343, filed Jan. 24, 1992 by Sarkiss Zoumalan and also assigned to the assignee of the present invention. The method described in the Zoumalan application overcomes some of the problems associated with testing gasolines to which oxygenates have been added but also requires the use of certain test liquids and sophisticated composition analysis equipment. Accordingly, the complexities found. in both of the above-mentioned test methods are not advantageous when it is desired to test gasolines for adulteration in the field, that is at bulk storage terminals or at the storage tanks for retail dispensing stations. It is to this end that the discovery and method of the present invention overcomes some of the problems associated with testing automotive motor gasolines for improper mixing or adulteration, particularly at various distribution and dispensing facilities.